how to create a separate copy of properties in ember js

After my latest update of ember-cli to 0.1.12 array.slice and jquery.extend is not creating a separate copy of arrays and objects.

Eg:

//Arrays
{
arrayProp: [a,b,c],

someFunction: function () {
    var localArrayProp = this.get('arrayProp').slice(0);
    localArrayProp.push('d');
/*
Now both arrayProp and localArrayProp will be a,b,c,d

This was not the case before updating, before updating arrayProp was a,b,c and localArrayProp was a,b,c,d
*/    
    }
}

//objects
    {
    objectProp: {'key1':'val1', 'key2':'val2'},

    someFunction: function () {
        var localObjectProp = $.extend({},this.get('objectProp'));
        localObjectProp.key3 = 'val3';
    /*
    Now both objectProp and localObjectProp will be {'key1':'val1', 'key2':'val2', 'key3':'val3'}

    This was not the case before updating, before updating objectProp was {'key1':'val1', 'key2':'val2'} and localObjectProp was {'key1':'val1', 'key2':'val2', 'key3':'val3'}
    */


        }
    }

Also now how to obtain the above.A bit urgent please!